1. Field of the Invention
The present invention relates to a semiconductor device formed by burying a gate electrode in a trench (trench-gate semiconductor device) and a manufacturing method thereof, and more particularly, to a trench-gate semiconductor device suitable to ensure avalanche tolerance while reducing on-resistance and a manufacturing method of the same.
2. Description of the Related Art
Trench-gate semiconductor devices are required to sufficiently lower a generated voltage in an on-state (on-voltage) to reduce loss and so forth, and this is especially required for power application generally. For this purpose, for example, it is effective to increase density of a channel region by narrowing the pitch between plural provided gate electrodes. Further, it is also effective to adopt a structure in which the region positioned to face the gate electrode becomes the channel region as well as possible.
However, when the microfabrication or the structure as described above is performed or adopted, it becomes difficult to form a contact layer for keeping a base layer, which is to be the channel region, at a voltage of a lower electric potential side electrode from the viewpoint of ensuring an area to form the contact layer. Further, since there is no other choice but to reduce the area of the contact layer itself, it is difficult to form a deep region, and possible to lose assured contact with the base layer existing under. When the contact with the base layer is not assured, the potential of the base layer floats from the potential of the lower electric potential side electrode, in which a parasitic transistor is turn on to thereby reduce avalanche tolerance.
Note that there is disclosed one in a below patent document 1, which has externally almost the same problem to be solved as of the trench-gate semiconductor device disclosed in the present application, whereas the one has a structure different from that of the trench-gate semiconductor device disclosed in the present application.
[Patent document 1] JP-A 2005-79448 (KOKAI)